I have a large geographic area where I would like to delineate playa areas for future use. I am aware of the NHD data sets contains playas but I want a more refined and detailed playa areas, as this data set only seems to contain the very large ones and I am unsure what their methodology in identifying them is. Is there a way using spatial analyst that I could delineate the sink areas in a dem and extrapolate a polygon area indicating a rough playa polygon boundary? I have used the sink function within spatial analyst but its only identifying specks in my dem wheres as I would like it to indicate areas where there are contour depressions. Any suggestions?
Mapping Center Answer:
We have experimented with the approach you thought of, as well as others, but we ultimately came to the conclusion that the fastest and most accurate way to capture these features is to digitize them. We digitize them as polygons using primarily USGS quads as our source. For many physiographic features we have digitized the feature simply to be able to add the label. But for playas, you will most likley also want to symboloze them. therefore, you want a good representation of their extent.
I am not sure how large an extent you are digitizing, or what part of the world you are working in, but there is a physiographic features data set that you can download from our ArcGIS Resources - GIS Data page -- it might have the extent and resolution you need, or it might now. Also, there are physiographic features in the VMAP data.
We wrote about all of this in our paper titled, "A Data Model for Named Features of the Natural Landscape" which you can access on our Other Resources - Publications page of Mapping Center.
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